U.S. patent number 11,259,248 [Application Number 16/131,276] was granted by the patent office on 2022-02-22 for handling power transitions in new radio.
This patent grant is currently assigned to QUALCOMM Incorporated. The grantee listed for this patent is QUALCOMM Incorporated. Invention is credited to Sony Akkarakaran, Peter Gaal, Yi Huang, Tao Luo, Alexandros Manolakos, Seyong Park, Renqiu Wang.
United States Patent |
11,259,248 |
Akkarakaran , et
al. |
February 22, 2022 |
Handling power transitions in new radio
Abstract
Aspects of the present disclosure provide techniques for
handling power transitions in transmissions in new radio (NR)
devices. An exemplary method includes changing from using a first
transmit power during a first portion of a transmission to a second
transmit power during a second portion of the transmission, and
taking action to mitigate a potential phase coherence loss
associated with the changing from the first transmit power to the
second transmit power.
Inventors: |
Akkarakaran; Sony (Poway,
CA), Huang; Yi (San Diego, CA), Wang; Renqiu (San
Diego, CA), Park; Seyong (San Diego, CA), Luo; Tao
(San Diego, CA), Gaal; Peter (San Diego, CA), Manolakos;
Alexandros (San Diego, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
|
|
Assignee: |
QUALCOMM Incorporated (San
Diego, CA)
|
Family
ID: |
65721164 |
Appl.
No.: |
16/131,276 |
Filed: |
September 14, 2018 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20190090201 A1 |
Mar 21, 2019 |
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Foreign Application Priority Data
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Sep 18, 2017 [GR] |
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20170100419 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W
52/146 (20130101); H04W 52/346 (20130101); H04W
76/27 (20180201); H04L 27/2614 (20130101); H04L
5/0007 (20130101); H04W 52/24 (20130101); H04L
5/0053 (20130101); H04L 5/0051 (20130101); H04L
5/0091 (20130101); H04W 52/325 (20130101); H04L
5/0073 (20130101) |
Current International
Class: |
H04W
72/00 (20090101); H04W 52/24 (20090101); H04W
76/27 (20180101); H04L 5/00 (20060101); H04W
52/14 (20090101); H04W 52/34 (20090101); H04L
27/26 (20060101); H04W 52/32 (20090101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO-2015023220 |
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Feb 2015 |
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WO |
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Other References
International Search Report and Written
Opinion--PCT/US2018/051253--ISA/EPO--dated Feb. 20, 2019. cited by
applicant .
Taiwan Search Report--TW107132596--TIPO--dated Oct. 14, 2021. cited
by applicant.
|
Primary Examiner: Ko; Sithu
Attorney, Agent or Firm: Patterson & Sheridan, LLP
Claims
What is claimed is:
1. A method for wireless communications, comprising: determining to
use a first transmit power during a first portion of a physical
uplink shared channel (PUSCH) transmission and a second transmit
power during a second portion of the PUSCH transmission, the second
transmit power different from the first transmit power; mitigating
a potential phase coherence loss associated with changing from
transmitting the first portion of the PUSCH transmission at the
first transmit power to transmitting the second portion of the
PUSCH transmission at the second transmit power different from the
first transmit power, wherein mitigating the potential phase
coherence loss comprises blanking one or more resource elements
(REs) in a digital domain signal for the PUSCH transmission prior
to converting the digital domain signal for the PUSCH transmission
to an analog domain signal for the PUSCH transmission; and
transmitting the first portion of the PUSCH transmission using the
first transmit power and the second portion of the PUSCH
transmission using the second transmit power different from the
first transmit power.
2. The method of claim 1, wherein mitigating the potential phase
coherence loss comprises blanking an orthogonal frequency domain
multiplexing (OFDM) symbol in the PUSCH transmission.
3. The method of claim 1, wherein mitigating the potential phase
coherence loss further comprises: boosting a power level of one or
more other REs.
4. The method of claim 3, wherein boosting the power level of the
one or more other REs comprises boosting the power level of the one
or more REs in the digital domain signal prior to converting the
digital domain signal to the analog domain signal.
5. The method of claim 3, further comprising: sending an indication
of the power level.
6. The method of claim 5, wherein the indication is sent via an
uplink (UL) control signal.
7. The method of claim 6, further comprising: receiving a downlink
control channel scheduling the UL control signal.
8. The method of claim 1, wherein mitigating the potential phase
coherence loss further comprises: selecting a sequence for a
demodulation reference signal (DMRS) of the PUSCH transmission with
a peak-to-average-power-ratio (PAPR) less than or equal to a PAPR
of a low PAPR waveform for conveying data in the PUSCH
transmission.
9. The method of claim 8, wherein the low PAPR waveform uses pi/2
binary phase shift keying (pi/2-BPSK) modulation with a discrete
Fourier transform single-carrier orthogonal frequency division
multiplexing (DFT-s-OFDM) waveform.
10. The method of claim 8, wherein the low PAPR waveform uses
modifications to allow the low PAPR to be preserved when the low
PAPR waveform occupies an interleaved set of frequency tones or
occupies multiple orthogonal frequency division multiplexing (OFDM)
symbols across which an orthogonal cover code is applied.
11. The method of claim 8, further comprising: deriving a pattern
and an overhead of the DMRS based on a combination of: radio
resource control (RRC) signaling, and an implicit determination
that is based on at least one of a modulation and coding scheme
(MCS) and a waveform for conveying the data.
12. The method of claim 1, wherein the first portion of the PUSCH
transmission comprises a demodulation reference signal (DMRS), and
wherein mitigating the potential phase coherence loss further
comprises: applying a different power amplifier (PA) backoff for
the first portion of the PUSCH transmission than another PA backoff
for the second portion of the PUSCH transmission.
13. The method of claim 1, wherein the first portion of the PUSCH
transmission comprises a demodulation reference signal (DMRS), and
wherein mitigating the potential phase coherence loss further
comprises: applying a fixed power ratio between a power for the
DMRS and a power for the second portion of the PUSCH
transmission.
14. The method of claim 13, wherein applying the fixed power ratio
between the DMRS power and the power of the second portion of the
PUSCH transmission comprises applying the fixed power ratio between
the DMRS power and the power of the second portion of the PUSCH
transmission regardless of an available power headroom remaining at
a power amplifier (PA) output.
15. The method of claim 1, wherein: the first portion of the PUSCH
transmission comprises a demodulation reference signal (DMRS); and
the second portion of the PUSCH transmission comprises a data
portion.
16. An apparatus for wireless communications, comprising: a
processor configured to: determine to use a first transmit power
during a first portion of a physical uplink shared channel (PUSCH)
transmission and a second transmit power during a second portion of
the PUSCH transmission, the second transmit power different from
the first transmit power; mitigate a potential phase coherence loss
associated with changing from transmitting the first portion of the
PUSCH transmission at the first transmit power to transmitting the
second portion of the PUSCH transmission at the second transmit
power different from the first transmit power, wherein the
processor being configured to mitigate the potential phase
coherence loss comprises the processor being configured to blank
one or more resource elements (REs) in a digital domain signal for
the PUSCH transmission prior to converting the digital domain
signal for the PUSCH transmission to an analog domain signal for
the PUSCH transmission; and transmit the first portion of the PUSCH
transmission using the first transmit power and the second portion
of the PUSCH transmission using the second transmit power different
from the first transmit power; and a memory coupled with the
processor.
17. The apparatus of claim 16, wherein: the first portion of the
PUSCH transmission comprises a demodulation reference signal
(DMRS); and the second portion of the PUSCH transmission comprises
a data portion.
18. The apparatus of claim 16, wherein the processor being
configured to mitigate the potential phase coherence loss comprises
the processor being configured to blank an orthogonal frequency
domain multiplexing (OFDM) symbol in the PUSCH transmission.
19. The apparatus of claim 16 wherein the processor being
configured to mitigate the potential phase coherence loss comprises
the processing being configured to boost a power level of one or
more other REs.
20. The apparatus of claim 19, wherein the processor being
configured to boost the power level of the one or more other REs
comprises the processor being configured to boost the power level
of the one or more REs in the digital domain signal prior to
converting the digital domain signal to the analog domain
signal.
21. The apparatus of claim 19, wherein the processor is configured
to: send an indication of the power level.
22. The apparatus of claim 21, wherein the processor is configured
to: send the indication via an uplink (UL) control signal.
23. The apparatus of claim 22, wherein the processor is configured
to: receive a downlink control channel scheduling the UL control
signal.
24. The apparatus of claim 16, wherein the processor being
configured to mitigate the potential phase coherence loss comprises
the processor being configured to: select a sequence for a
demodulation reference signal (DMRS) of the PUSCH transmission with
a peak-to-average-power-ratio (PAPR) less than or equal to a PAPR
of a low PAPR waveform for conveying data in the PUSCH
transmission.
25. The apparatus of claim 24, wherein: the low PAPR waveform uses
pi/2 binary phase shift keying (pi/2-BPSK) modulation with a
discrete Fourier transform single-carrier orthogonal frequency
division multiplexing (DFT-s-OFDM) waveform; and the processor is
configured to transmit at least one of the first portion of the
PUSCH transmission and the second portion of the PUSCH transmission
using the low PAPR waveform.
26. The apparatus of claim 24, wherein: the low PAPR waveform uses
modifications to allow the low PAPR to be preserved when the low
PAPR waveform occupies an interleaved set of frequency tones or
occupies multiple orthogonal frequency division multiplexing (OFDM)
symbols across which an orthogonal cover code is applied; and the
processor is configured to transmit at least one of the first
portion of the PUSCH transmission and the second portion of the
PUSCH transmission using the low PAPR waveform.
27. The apparatus of claim 24, wherein the processor is further
configured to: determine an implicit derivation of a pattern and a
potential overhead of the DMRS based on at least one of a
modulation and coding scheme (MCS) and a waveform for conveying the
data; and derive the pattern and overhead of the DMRS based on a
combination of: radio resource control (RRC) signaling, and the
implicit derivation.
28. The apparatus of claim 16, wherein the first portion of the
PUSCH transmission comprises a demodulation reference signal
(DMRS), and wherein the processor is configured to mitigate the
potential phase coherence loss by: applying a different power
amplifier (PA) backoff for the first portion of the PUSCH
transmission than another PA backoff for the second portion of the
PUSCH transmission.
29. The apparatus of claim 16, wherein the first portion of the
PUSCH transmission comprises a demodulation reference signal
(DMRS), and wherein the processor is configured to mitigate the
potential phase coherence loss by: applying a fixed power ratio
between a power for the DMRS and a power for the second portion of
the PUSCH transmission.
30. The apparatus of claim 29, wherein the processor is configured
to apply the fixed power ratio between the DMRS power and the power
of the second portion of the PUSCH transmission by applying the
fixed power ratio between the DMRS power and the power of the
second portion of the PUSCH transmission regardless of an available
power headroom remaining at a power amplifier (PA) output.
31. An apparatus for wireless communications, comprising: means for
determining to use a first transmit power during a first portion of
a physical uplink shared channel (PUSCH) transmission and a second
transmit power during a second portion of the PUSCH transmission,
the second transmit power different from the first transmit power;
means for mitigating a potential phase coherence loss associated
with changing from transmitting the first portion of the PUSCH
transmission at the first transmit power to transmitting the second
portion of the PUSCH transmission at the second transmit power
different from the first transmit power, wherein means for
mitigating the potential phase coherence loss comprises means for
blanking one or more resource elements (REs) in a digital domain
signal for the PUSCH transmission prior to converting the digital
domain signal for the PUSCH transmission to an analog domain signal
for the PUSCH transmission; and means for transmitting the first
portion of the PUSCH transmission using the first transmit power
and the second portion of the PUSCH transmission using the second
transmit power different from the first transmit power.
32. A non-transitory computer-readable medium having computer
executable code stored thereon for: determining to use a first
transmit power during a first portion of a physical uplink shared
channel (PUSCH) transmission and a second transmit power during a
second portion of the PUSCH transmission, the second transmit power
different from the first transmit power; mitigating a potential
phase coherence loss associated with changing from transmitting the
first portion of the PUSCH transmission at the first transmit power
to transmitting the second portion of the PUSCH transmission at the
second transmit power different from the first transmit power,
wherein mitigating the potential phase coherence loss comprises
blanking one or more resource elements (REs) in a digital domain
signal for the PUSCH transmission prior to converting the digital
domain signal for the PUSCH transmission to an analog domain signal
for the PUSCH transmission; and transmitting the first portion of
the PUSCH transmission using the first transmit power and the
second portion of the PUSCH transmission using the second transmit
power different from the first transmit power.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
The present Application for patent claims priority to Greek
Application No. 20170100419, filed Sep. 18, 2017, which is assigned
to the assignee hereof and hereby expressly incorporated by
reference herein in its entirety.
INTRODUCTION
Aspects of the present disclosure relate to wireless communications
and, more particularly, to handling power transitions by a wireless
communications device transmitting in a new radio (NR)
communications system, such as mitigating phase coherence losses
caused by changing a power level of a transmitter.
Wireless communication systems are widely deployed to provide
various telecommunication services such as telephony, video, data,
messaging, and broadcasts. Typical wireless communication systems
may employ multiple-access technologies capable of supporting
communication with multiple users by sharing available system
resources (e.g., bandwidth, transmit power). Examples of such
multiple-access technologies include Long Term Evolution (LTE)
systems, code division multiple access (CDMA) systems, time
division multiple access (TDMA) systems, frequency division
multiple access (FDMA) systems, orthogonal frequency division
multiple access (OFDMA) systems, single-carrier frequency division
multiple access (SC-FDMA) systems, and time division synchronous
code division multiple access (TD-SCDMA) systems.
A wireless communication network may include a number of Node Bs
that can support communication for a number of user equipments
(UEs). A UE may communicate with a Node B via the downlink and
uplink. The downlink (or forward link) refers to the communication
link from the Node B to the UE, and the uplink (or reverse link)
refers to the communication link from the UE to the Node B.
It may be desirable for transmitters in an NR (e.g., 5.sup.th
Generation Technology Forum (5GTF)) wireless communications system
to change a power level in the middle of transmissions. Changing a
power level in the middle of a transmission may cause a loss of
phase coherence (e.g., of the transmitted waveform). For example,
phase coherence may be lost if a power change is not implemented
digitally, but is instead implemented via a change in an analog
gain stage(s). Loss of phase coherence may be more severe in uplink
(UL) transmissions than in downlink (DL) transmissions, because
mobile devices (e.g., UEs) may have implementation constraints that
base stations (e.g., next generation NodeBs (gNBs)) do not have.
For example, an amount of digital gain that a mobile device can
generate may be less than an amount of digital gain that a base
station can generate.
SUMMARY
The systems, methods, and devices of the disclosure each have
several aspects, no single one of which is solely responsible for
its desirable attributes. Without limiting the scope of this
disclosure as expressed by the claims which follow, some features
will now be discussed briefly. After considering this discussion,
and particularly after reading the section entitled "Detailed
Description" one will understand how the features of this
disclosure provide advantages that include improved communications
between access points and stations in a wireless network.
Techniques for mitigating phase coherence loss by a wireless
communications device transmitting in a new radio (NR, e.g., a
5.sup.th generation (5G)) communications system are described
herein.
In an aspect, a method for wireless communication is provided. The
method may be performed, for example, by a wireless device. The
method generally includes determining to use a first transmit power
during a first portion of a transmission and a second transmit
power during a second portion of the transmission, mitigating a
potential phase coherence loss associated with a changing from the
first transmit power to the second transmit power, and transmitting
the first portion of the transmission using the first transmit
power and the second portion of the transmission using the second
transmit power.
In an aspect, a method for wireless communication is provided. The
method may be performed, for example, by a base station (BS). The
method generally includes transmitting a first grant scheduling a
user equipment (UE) to transmit a first transmission, wherein the
UE changes from using a first transmit power during a first portion
of the first transmission to a second transmit power during a
second portion of the first transmission, transmitting a second
grant scheduling the UE to transmit a second transmission
comprising an indication of at least one of the first transmit
power or the second transmit power, and receiving the first
transmission from the UE, based on the indication.
In an aspect, an apparatus for wireless communication is provided.
The apparatus generally includes a processor configured to
determine to use a first transmit power during a first portion of a
transmission and a second transmit power during a second portion of
the transmission, to mitigate a potential phase coherence loss
associated with a changing from the first transmit power to the
second transmit power, and to transmit the first portion of the
transmission using the first transmit power and the second portion
of the transmission using the second transmit power, and a memory
coupled with the processor.
In an aspect, an apparatus for wireless communication is provided.
The apparatus generally includes a processor configured to:
transmit a first grant scheduling a user equipment (UE) to transmit
a first transmission, wherein the UE changes from using a first
transmit power during a first portion of the first transmission to
a second transmit power during a second portion of the first
transmission, to transmit a second grant scheduling the UE to
transmit a second transmission comprising an indication of at least
one of the first transmit power or the second transmit power, and
to receive the first transmission from the UE, based on the
indication, and a memory coupled with the processor.
In an aspect, an apparatus for wireless communication is provided.
The method generally includes means for determining to use a first
transmit power during a first portion of a transmission and a
second transmit power during a second portion of the transmission,
means for mitigating a potential phase coherence loss associated
with a changing from the first transmit power to the second
transmit power, and means for transmitting the first portion of the
transmission using the first transmit power and the second portion
of the transmission using the second transmit power.
In an aspect, an apparatus for wireless communication is provided.
The apparatus generally includes means for transmitting a first
grant scheduling a user equipment (UE) to transmit a first
transmission, wherein the UE changes from using a first transmit
power during a first portion of the first transmission to a second
transmit power during a second portion of the first transmission,
means for transmitting a second grant scheduling the UE to transmit
a second transmission comprising an indication of at least one of
the first transmit power or the second transmit power, and means
for receiving the first transmission from the UE, based on the
indication.
In an aspect, a computer-readable medium for wireless communication
is provided. The computer-readable medium includes instructions
that, when executed by a processor, cause the processor to perform
operations generally including determining to use a first transmit
power during a first portion of a transmission and a second
transmit power during a second portion of the transmission,
mitigating a potential phase coherence loss associated with a
changing from the first transmit power to the second transmit
power, and transmitting the first portion of the transmission using
the first transmit power and the second portion of the transmission
using the second transmit power.
In an aspect, a computer-readable medium for wireless communication
is provided. The computer-readable medium includes instructions
that, when executed by a processor, cause the processor to perform
operations generally including transmitting a first grant
scheduling a user equipment (UE) to transmit a first transmission,
wherein the UE changes from using a first transmit power during a
first portion of the first transmission to a second transmit power
during a second portion of the first transmission, transmitting a
second grant scheduling the UE to transmit a second transmission
comprising an indication of at least one of the first transmit
power or the second transmit power, and receiving the first
transmission from the UE, based on the indication.
To the accomplishment of the foregoing and related ends, the one or
more aspects comprise the features hereinafter fully described and
particularly pointed out in the claims. The following description
and the drawings set forth in detail certain illustrative features
of the one or more aspects. These features are indicative, however,
of but a few of the various ways in which the principles of various
aspects may be employed, and this description is intended to
include all such aspects and their equivalents.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above-recited features of the
present disclosure can be understood in detail, a more particular
description, briefly summarized above, may be had by reference to
aspects, some of which are illustrated in the appended drawings. It
is to be noted, however, that the appended drawings illustrate only
certain typical aspects of this disclosure and are therefore not to
be considered limiting of its scope, for the description may admit
to other equally effective aspects.
FIG. 1 is a block diagram conceptually illustrating an example
telecommunications system, according to aspects of the present
disclosure.
FIG. 2 is a block diagram conceptually illustrating an example
downlink frame structure in a telecommunications system, according
to aspects of the present disclosure.
FIG. 3 is a diagram illustrating an example uplink frame structure
in a telecommunications system, according to aspects of the present
disclosure.
FIG. 4 is a block diagram conceptually illustrating a design of an
example Node B and user equipment (UE), according to aspects of the
present disclosure.
FIG. 5 is a block diagram of an example transceiver front end, in
accordance with certain aspects of the present disclosure.
FIG. 6 is a diagram illustrating an example radio protocol
architecture for the user and control planes, according to aspects
of the present disclosure.
FIG. 7 illustrates an example subframe resource element mapping,
according to aspects of the present disclosure.
FIG. 8 illustrates an example of a DL-centric subframe, in
accordance with certain aspects of the present disclosure.
FIG. 9 illustrates an example of an UL-centric subframe, in
accordance with certain aspects of the present disclosure.
FIGS. 10A-10C illustrate exemplary transmission timelines,
according to aspects of the present disclosure.
FIG. 11 illustrates an example of an uplink transmission, according
to aspects of the present disclosure.
FIG. 12 illustrates example operations that may be performed by a
wireless device, according to aspects of the present
disclosure.
FIG. 13 illustrates example operations that may be performed by a
BS, according to aspects of the present disclosure.
To facilitate understanding, identical reference numerals have been
used, where possible, to designate identical elements that are
common to the figures. It is contemplated that elements disclosed
in one aspect may be beneficially utilized on other aspects without
specific recitation.
DETAILED DESCRIPTION
Aspects of the present disclosure provide apparatus, methods,
processing systems, and computer readable mediums for handling
power transitions in new radio (NR) wireless communications
systems. According to aspects of the present disclosure described
herein, a device may transmit a transmission with different power
levels for different portions of the transmission (e.g., different
power levels for reference signals and data incorporated in an
orthogonal frequency domain multiplexing (OFDM) symbol), and the
device may take one or more actions to mitigate a phase coherence
loss that may result from the changing power level of the
transmission. A phase coherence loss may cause a receiver to
experience difficulty in receiving and decoding the transmission,
so mitigating the potential phase coherence may improve data
throughput rates and/or reduce error rates of communications.
Various aspects of the disclosure are described more fully
hereinafter with reference to the accompanying drawings. This
disclosure may, however, be embodied in many different forms and
should not be construed as limited to any specific structure or
function presented throughout this disclosure. Rather, these
aspects are provided so that this disclosure will be thorough and
complete, and will fully convey the scope of the disclosure to
those skilled in the art. Based on the teachings herein one skilled
in the art should appreciate that the scope of the disclosure is
intended to cover any aspect of the disclosure disclosed herein,
whether implemented independently of or combined with any other
aspect of the disclosure. For example, an apparatus may be
implemented or a method may be practiced using any number of the
aspects set forth herein. In addition, the scope of the disclosure
is intended to cover such an apparatus or method which is practiced
using other structure, functionality, or structure and
functionality in addition to or other than the various aspects of
the disclosure set forth herein. It should be understood that any
aspect of the disclosure disclosed herein may be embodied by one or
more elements of a claim.
The word "exemplary" is used herein to mean "serving as an example,
instance, or illustration." Any aspect described herein as
"exemplary" is not necessarily to be construed as preferred or
advantageous over other aspects.
Although particular aspects are described herein, many variations
and permutations of these aspects fall within the scope of the
disclosure. Although some benefits and advantages of the preferred
aspects are mentioned, the scope of the disclosure is not intended
to be limited to particular benefits, uses, or objectives. Rather,
aspects of the disclosure are intended to be broadly applicable to
different wireless technologies, system configurations, networks,
and transmission protocols, some of which are illustrated by way of
example in the figures and in the following description of the
preferred aspects. The detailed description and drawings are merely
illustrative of the disclosure rather than limiting and the scope
of the disclosure is being defined by the appended claims and
equivalents thereof.
The techniques described herein may be used for various wireless
communication networks such as LTE, CDMA, TDMA, FDMA, OFDMA,
SC-FDMA and other networks. The terms "network" and "system" are
often used interchangeably. A CDMA network may implement a radio
technology such as Universal Terrestrial Radio Access (UTRA),
cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other
variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856
standards. A TDMA network may implement a radio technology such as
Global System for Mobile Communications (GSM). An OFDMA network may
implement a radio technology such as NR (e.g. 5G RA), Evolved UTRA
(E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE
802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are
part of Universal Mobile Telecommunication System (UMTS). NR is an
emerging wireless communications technology under development in
conjunction with the 5G Technology Forum (5GTF). 3GPP Long Term
Evolution (LTE) and LTE-Advanced (LTE-A) are releases of UMTS that
use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in
documents from an organization named "3rd Generation Partnership
Project" (3GPP). cdma2000 and UMB are described in documents from
an organization named "3rd Generation Partnership Project 2"
(3GPP2). The techniques described herein may be used for the
wireless networks and radio technologies mentioned above as well as
other wireless networks and radio technologies.
For clarity, while aspects may be described herein using
terminology commonly associated with 3G and/or 4G wireless
technologies, aspects of the present disclosure can be applied in
other generation-based communication systems, such as 5G and later,
including NR technologies.
New radio (NR) may refer to radios configured to operate according
to a new air interface (e.g., other than Orthogonal Frequency
Divisional Multiple Access (OFDMA)-based air interfaces) or fixed
transport layer (e.g., other than Internet Protocol (IP)). NR may
include Enhanced mobile broadband (eMBB) techniques targeting wide
bandwidth (e.g., 80 MHz and wider) communications, millimeter wave
(mmW) techniques targeting high carrier frequency (e.g., 27 GHz and
higher) communications, massive machine type communications (mMTC)
techniques targeting non-backward compatible machine type
communications (MTC), and mission critical techniques targeting
ultra reliable low latency communications (URLLC). For these
general topics, different techniques are considered, such as
coding, including low-density parity check (LDPC) coding, and polar
coding. NR cell may refer to a cell operating according to the new
air interface or fixed transport layer. A NR Node B (e.g., a 5G
Node B) may correspond to one or multiple transmission reception
points (TRPs).
NR cells can be configured as access cell (ACells) or data only
cells (DCells). For example, the radio access network (e.g., a
central unit or distributed unit) can configure the cells. DCells
may be cells used for carrier aggregation or dual connectivity, but
not used for initial access, cell selection/reselection, or
handover. In some cases DCells may not transmit synchronization
signals (SS)--in some case cases DCells may transmit SS. TRPs may
transmit downlink signals to UEs indicating the cell type. Based on
the cell type indication, the UE may communicate with the TRP. For
example, the UE may determine TRPs to consider for cell selection,
access, handover, and/or measurement based on the indicated cell
type.
In some cases, the UE can receive measurement configuration from
the radio access network (RAN). The measurement configuration
information may indicate ACells or DCells for the UE to measure.
The UE may monitor and/or detect measurement reference signals
(MRS) from the cells based on measurement configuration
information. In some cases, the UE may blindly detect MRS. In some
cases the UE may detect MRS based on MRS identifiers (MRS-IDs)
indicated from the RAN. The UE may report the measurement
results.
Example Wireless Communications System
FIG. 1 illustrates an example wireless network 100 in which aspects
of the present disclosure may be performed. For example, the
wireless network may be a new radio (NR) or a 5G network.
According to aspects, the wireless network 100 may be a
heterogeneous numerology system, wherein UEs 120 within the network
100 may be asynchronous, have different intercarrier spacing,
and/or have different cyclic prefix lengths. According to aspects a
BS, such as BS 110a may support different services having different
service requirements. For example, the BS 110a may support subframe
with different subcarrier spacing. The BS 110a may communicate with
UE 120a using a first subcarrier spacing and may communicate with
UE 120b using a second subcarrier spacing. UEs 120a, 120b may be
configured to operate according to one or more numerologies. In the
manner a network may support subframes with different subcarrier
spacings.
According to aspects, the subcarrier spacing associated with the
different service requirements may be scaled. As a non-limiting
example, for illustrative purposes only, the subcarrier spacing may
be 15 kHz, 30 kHz, 60 kHz, 120 kHz, and so on (e.g., x1, x2, x4,
x8, and so on . . . ). According to another example, the subcarrier
spacing may be 17.5 kHz, 35 kHz, and so on (e.g., x1, x2, x3, x4,
and so on). Aspects described herein provide methods for tone
allocation and resource block definition for heterogeneous
numerology systems, which may be beneficial for scheduling devices
and communicating with one or more devices in heterogeneous
numerology systems.
As described herein, a numerology may be based, at least in part,
on a subcarrier spacing and a shift in frequency. The BS 110a and
UE 120a may communicate using tones determined using a numerology.
Additionally or alternatively, the BS 110a and 120a may communicate
using an RB defined using a numerology.
According to some aspects of the present disclosure, the UE 120 may
change from using a first transmit power during a first portion of
a transmission to a second transmit power during a second portion
of the transmission and take action to mitigate a potential phase
coherence loss associated with the changing from the first transmit
power to the second transmit power, as described herein with
reference to FIG. 12.
According to some aspects of the present disclosure, the BS 110 may
be configured to transmit a first grant scheduling a UE (e.g., UE
120) to transmit a first transmission, wherein the UE changes from
using a first transmit power during a first portion of the first
transmission to a second transmit power during a second portion of
the first transmission; to transmit a second grant scheduling the
UE to transmit a second transmission comprising an indication of at
least one of the first transmit power or the second transmit power;
and to receive the first transmission from the UE, based on the
indication, as described herein with reference to FIG. 13.
Furthermore, the BS 110 and the UE 120 may be configured to perform
other aspects described herein, such as changing from using a first
transmit power during a first portion of a transmission to a second
transmit during a second portion of the transmission and taking
action to mitigate a potential phase coherence loss associated with
changing the transmit power, described below with reference to FIG.
12. The BS may comprise and/or include a transmission reception
point (TRP).
The system illustrated in FIG. 1 may be, for example, a 5G network.
The wireless network 100 may include a number of Node Bs (e.g.,
eNodeBs, eNBs, 5G Node B, etc.) 110 and other network entities. A
Node B may be a station that communicates with the UEs and may also
be referred to as a base station, an access point, or a 5G Node
B.
Each Node B 110 may provide communication coverage for a particular
geographic area. In 3GPP and NR systems, the term "cell" can refer
to a coverage area of a Node B and/or a Node B subsystem serving
this coverage area, depending on the context in which the term is
used.
A Node B may provide communication coverage for a macro cell, a
pico cell, a femto cell, and/or other types of cell. A macro cell
may cover a relatively large geographic area (e.g., several
kilometers in radius) and may allow unrestricted access by UEs with
service subscription. A pico cell may cover a relatively small
geographic area and may allow unrestricted access by UEs with
service subscription. A femto cell may cover a relatively small
geographic area (e.g., a home) and may allow restricted access by
UEs having association with the femto cell (e.g., UEs in a Closed
Subscriber Group (CSG), UEs for users in the home, etc.). A Node B
for a macro cell may be referred to as a macro Node B. A Node B for
a pico cell may be referred to as a pico Node B. A Node B for a
femto cell may be referred to as a femto Node B or a home Node B.
In the example shown in FIG. 1, the Node Bs 110a, 110b and 110c may
be macro Node Bs for the macro cells 102a, 102b and 102c,
respectively. The Node B 110x may be a pico Node B for a pico cell
102x. The Node Bs 110y and 110z may be femto Node Bs for the femto
cells 102y and 102z, respectively. A Node B may support one or
multiple (e.g., three) cells.
The wireless network 100 may also include relay stations. A relay
station is a station that receives a transmission of data and/or
other information from an upstream station (e.g., a Node B or a UE)
and sends a transmission of the data and/or other information to a
downstream station (e.g., a UE or a Node B). A relay station may
also be a UE that relays transmissions for other UEs. In the
example shown in FIG. 1, a relay station 110r may communicate with
the Node B 110a and a UE 120r in order to facilitate communication
between the Node B 110a and the UE 120r. A relay station may also
be referred to as a relay Node B, a relay, etc.
The wireless network 100 may be a heterogeneous network that
includes Node Bs of different types, e.g., macro Node Bs, pico Node
Bs, femto Node Bs, relays, transmission reception points (TRPs),
etc. These different types of Node Bs may have different transmit
power levels, different coverage areas, and different impact on
interference in the wireless network 100. For example, macro Node
Bs may have a high transmit power level (e.g., 20 Watts) whereas
pico Node Bs, femto Node Bs and relays may have a lower transmit
power level (e.g., 1 Watt).
The wireless network 100 may support synchronous or asynchronous
operation. For synchronous operation, the Node Bs may have similar
frame timing, and transmissions from different Node Bs may be
approximately aligned in time. For asynchronous operation, the Node
Bs may have different frame timing, and transmissions from
different Node Bs may not be aligned in time. The techniques
described herein may be used for both synchronous and asynchronous
operation.
A network controller 130 may couple to a set of Node Bs and provide
coordination and control for these Node Bs. The network controller
130 may communicate with the Node Bs 110 via a backhaul. The Node
Bs 110 may also communicate with one another, e.g., directly or
indirectly via wireless or wireline backhaul.
The UEs 120 (e.g., 120x, 120y, etc.) may be dispersed throughout
the wireless network 100, and each UE may be stationary or mobile.
A UE may also be referred to as a terminal, a mobile station, a
subscriber unit, a station, etc. A UE may be a cellular phone, a
personal digital assistant (PDA), a wireless modem, a wireless
communication device, a handheld device, a laptop computer, a
cordless phone, a wireless local loop (WLL) station, a tablet, a
netbook, a smart book, etc. A UE may be able to communicate with
macro Node Bs, pico Node Bs, femto Node Bs, relays, etc. In FIG. 1,
a solid line with double arrows indicates desired transmissions
between a UE and a serving Node B, which is a Node B designated to
serve the UE on the downlink and/or uplink. A dashed line with
double arrows indicates interfering transmissions between a UE and
a Node B.
LTE utilizes orthogonal frequency division multiplexing (OFDM) on
the downlink and single-carrier frequency division multiplexing
(SC-FDM) on the uplink. OFDM and SC-FDM partition the system
bandwidth into multiple (K) orthogonal subcarriers, which are also
commonly referred to as tones, bins, etc. Each subcarrier may be
modulated with data. In general, modulation symbols are sent in the
frequency domain with OFDM and in the time domain with SC-FDM. The
spacing between adjacent subcarriers may be fixed, and the total
number of subcarriers (K) may be dependent on the system bandwidth.
For example, the spacing of the subcarriers may be 15 kHz and the
minimum resource allocation (called a `resource block`) may be 12
subcarriers (or 180 kHz). Consequently, the nominal FFT size may be
equal to 128, 256, 512, 1024 or 2048 for system bandwidth of 1.25,
2.5, 5, 10 or 20 megahertz (MHz), respectively. The system
bandwidth may also be partitioned into subbands. For example, a
subband may cover 1.08 MHz (i.e., 6 resource blocks), and there may
be 1, 2, 4, 8 or 16 subbands for system bandwidth of 1.25, 2.5, 5,
10 or 20 MHz, respectively. New radio (NR) may use a different air
interface, other than OFDM-based. NR networks may include entities
such central units or distributed units.
While aspects of the examples described herein may be associated
with LTE technologies, aspects of the present disclosure may be
applicable with other wireless communications systems, such as NR.
NR may utilize OFDM with a CP on the uplink and downlink and
include support for half-duplex operation using TDD. A single
component carrier bandwidth of 100 MHZ may be supported. NR
resource blocks may span 12 sub-carriers with a sub-carrier
bandwidth of 75 kHz over a 0.1 ms duration. Each radio frame may
consist of 2 half frames, each half frame consisting of 5
subframes, with a length of 10 ms. Consequently, each subframe may
have a length of 1 ms. Each subframe may indicate a link direction
(i.e., DL or UL) for data transmission and the link direction for
each subframe may be dynamically switched. Each subframe may
include DL/UL data as well as DL/UL control data. Beamforming may
be supported and beam direction may be dynamically configured. MIMO
transmissions with precoding may also be supported. MIMO
configurations in the DL may support up to 8 transmit antennas with
multi-layer DL transmissions up to 8 streams and up to 2 streams
per UE. Multi-layer transmissions with up to 2 streams per UE may
be supported. Aggregation of multiple cells may be supported with
up to 8 serving cells. Alternatively, NR may support a different
air interface, other than an OFDM-based. NR networks may include
entities such central units or distributed units.
FIG. 2 shows a down link (DL) frame structure used in a
telecommunication systems (e.g., LTE). The transmission timeline
for the downlink may be partitioned into units of radio frames.
Each radio frame may have a predetermined duration (e.g., 10
milliseconds (ms)) and may be partitioned into 10 sub-frames with
indices of 0 through 9. Each sub-frame may include two slots. Each
radio frame may thus include 20 slots with indices of 0 through 19.
Each slot may include L symbol periods, e.g., 7 symbol periods for
a normal cyclic prefix (as shown in FIG. 2) or 6 symbol periods for
an extended cyclic prefix. The 2L symbol periods in each sub-frame
may be assigned indices of 0 through 2L-1. The available time
frequency resources may be partitioned into resource blocks. Each
resource block may cover N subcarriers (e.g., 12 subcarriers) in
one slot.
In LTE, a Node B may send a primary synchronization signal (PSS)
and a secondary synchronization signal (SSS) for each cell in the
Node B. The primary and secondary synchronization signals may be
sent in symbol periods 6 and 5, respectively, in each of sub-frames
0 and 5 of each radio frame with the normal cyclic prefix, as shown
in FIG. 2. The synchronization signals may be used by UEs for cell
detection and acquisition. The Node B may send a Physical Broadcast
Channel (PBCH) in symbol periods 0 to 3 in slot 1 of sub-frame 0.
The PBCH may carry certain system information.
The Node B may send a Physical Control Format Indicator Channel
(PCFICH) in only a portion of the first symbol period of each
sub-frame, although depicted in the entire first symbol period in
FIG. 2. The PCFICH may convey the number of symbol periods (M) used
for control channels, where M may be equal to 1, 2 or 3 and may
change from sub-frame to sub-frame. M may also be equal to 4 for a
small system bandwidth, e.g., with less than 10 resource blocks. In
the example shown in FIG. 2, M=3. The Node B may send a Physical
HARQ Indicator Channel (PHICH) and a Physical Downlink Control
Channel (PDCCH) in the first M symbol periods of each sub-frame
(M=3 in FIG. 2). The PHICH may carry information to support hybrid
automatic retransmission (HARQ). The PDCCH may carry information on
uplink and downlink resource allocation for UEs and power control
information for uplink channels. Although not shown in the first
symbol period in FIG. 2, it is understood that the PDCCH and PHICH
are also included in the first symbol period. Similarly, the PHICH
and PDCCH are also both in the second and third symbol periods,
although not shown that way in FIG. 2. The Node B may send a
Physical Downlink Shared Channel (PDSCH) in the remaining symbol
periods of each sub-frame. The PDSCH may carry data for UEs
scheduled for data transmission on the downlink. The various
signals and channels in LTE are described in 3GPP TS 36.211,
entitled "Evolved Universal Terrestrial Radio Access (E-UTRA);
Physical Channels and Modulation," which is publicly available.
The Node B may send the PSS, SSS and PBCH in the center 1.08 MHz of
the system bandwidth used by the Node B. The Node B may send the
PCFICH and PHICH across the entire system bandwidth in each symbol
period in which these channels are sent. The Node B may send the
PDCCH to groups of UEs in certain portions of the system bandwidth.
The Node B may send the PDSCH to specific UEs in specific portions
of the system bandwidth. The Node B may send the PSS, SSS, PBCH,
PCFICH and PHICH in a broadcast manner to all UEs, may send the
PDCCH in a unicast manner to specific UEs, and may also send the
PDSCH in a unicast manner to specific UEs.
A number of resource elements may be available in each symbol
period. Each resource element may cover one subcarrier in one
symbol period and may be used to send one modulation symbol, which
may be a real or complex value. Resource elements not used for a
reference signal in each symbol period may be arranged into
resource element groups (REGs). Each REG may include four resource
elements in one symbol period. The PCFICH may occupy four REGs,
which may be spaced approximately equally across frequency, in
symbol period 0. The PHICH may occupy three REGs, which may be
spread across frequency, in one or more configurable symbol
periods. For example, the three REGs for the PHICH may all belong
in symbol period 0 or may be spread in symbol periods 0, 1 and 2.
The PDCCH may occupy 9, 18, 36 or 72 REGs, which may be selected
from the available REGs, in the first M symbol periods. Only
certain combinations of REGs may be allowed for the PDCCH.
A UE may know the specific REGs used for the PHICH and the PCFICH.
The UE may search different combinations of REGs for the PDCCH. The
number of combinations to search is typically less than the number
of allowed combinations for the PDCCH. A Node B may send the PDCCH
to the UE in any of the combinations that the UE will search.
A UE may be within the coverage of multiple Node Bs. One of these
Node Bs may be selected to serve the UE. The serving Node B may be
selected based on various criteria such as received power, path
loss, signal-to-noise ratio (SNR), etc.
FIG. 3 is a diagram 300 illustrating an example of an uplink (UL)
frame structure in a telecommunications system (e.g., LTE). The
available resource blocks for the UL may be partitioned into a data
section and a control section. The control section may be formed at
the two edges of the system bandwidth and may have a configurable
size. The resource blocks in the control section may be assigned to
UEs for transmission of control information. The data section may
include all resource blocks not included in the control section.
The UL frame structure results in the data section including
contiguous subcarriers, which may allow a single UE to be assigned
all of the contiguous subcarriers in the data section.
A UE may be assigned resource blocks 310a, 310b in the control
section to transmit control information to a Node B. The UE may
also be assigned resource blocks 320a, 320b in the data section to
transmit data to the Node B. The UE may transmit control
information in a physical UL control channel (PUCCH) on the
assigned resource blocks in the control section. The UE may
transmit only data or both data and control information in a
physical UL shared channel (PUSCH) on the assigned resource blocks
in the data section. A UL transmission may span both slots of a
subframe and may hop across frequency.
A set of resource blocks may be used to perform initial system
access and achieve UL synchronization in a physical random access
channel (PRACH) 330. The PRACH 330 carries a random sequence and
cannot carry any UL data/signaling. Each random access preamble
occupies a bandwidth corresponding to six consecutive resource
blocks. The starting frequency is specified by the network. That
is, the transmission of the random access preamble is restricted to
certain time and frequency resources. There is no frequency hopping
for the PRACH. The PRACH attempt is carried in a single subframe (1
ms) or in a sequence of few contiguous subframes and a UE can make
only a single PRACH attempt per frame (10 ms).
FIG. 4 illustrates example components of the base station 110 and
UE 120 illustrated in FIG. 1, which may be used to implement
aspects of the present disclosure. One or more components of the BS
110 and UE 120 may be used to practice aspects of the present
disclosure. For example, antennas 452, Tx/Rx 222, processors 466,
458, 464, and/or controller/processor 480 of the UE 120 and/or
antennas 434, processors 460, 420, 438, and/or controller/processor
440 of the BS 110 may be used to perform the operations described
herein and illustrated with reference to FIGS. 12-13. The BS 110
may comprise a TRP. As illustrated, the BS/TRP 110 and UE 120 may
communicate using tone alignment and/or RB definition in a
heterogeneous numerology system.
At the base station 110, a transmit processor 420 may receive data
from a data source 412 and control information from a
controller/processor 440. The control information may be for the
PBCH, PCFICH, PHICH, PDCCH, etc. The data may be for the PDSCH,
etc. The transmit processor 420 may process (e.g., encode and
symbol map) the data and control information to obtain data symbols
and control symbols, respectively. The transmit processor 420 may
also generate reference symbols, e.g., for the PSS, SSS, and
cell-specific reference signal. A transmit (TX) multiple-input
multiple-output (MIMO) processor 430 may perform spatial processing
(e.g., precoding) on the data symbols, the control symbols, and/or
the reference symbols, if applicable, and may provide output symbol
streams to the modulators (MODs) 432a through 432t. Each modulator
432 may process a respective output symbol stream (e.g., for OFDM,
etc.) to obtain an output sample stream. Each modulator 432 may
further process (e.g., convert to analog, amplify, filter, and
upconvert) the output sample stream to obtain a downlink signal.
Downlink signals from modulators 432a through 432t may be
transmitted via the antennas 434a through 434t, respectively. The
transmit processor 420, TX MIMO processor 430, modulators
432a-432t, and antennas 434a-434t may be collectively referred to
as a transmit chain of the base station.
At the UE 120, the antennas 452a through 452r may receive the
downlink signals from the base station 110 and may provide received
signals to the demodulators (DEMODs) 454a through 454r,
respectively. Each demodulator 454 may condition (e.g., filter,
amplify, downconvert, and digitize) a respective received signal to
obtain input samples. Each demodulator 454 may further process the
input samples (e.g., for OFDM, etc.) to obtain received symbols. A
MIMO detector 456 may obtain received symbols from all the
demodulators 454a through 454r, perform MIMO detection on the
received symbols if applicable, and provide detected symbols. A
receive processor 458 may process (e.g., demodulate, deinterleave,
and decode) the detected symbols, provide decoded data for the UE
120 to a data sink 460, and provide decoded control information to
a controller/processor 480. The receive processor 458, MIMO
detector 456, demodulators 454a-454r, and antennas 452a-452t may be
collectively referred to as a receive chain of the UE.
On the uplink, at the UE 120, a transmit processor 464 may receive
and process data (e.g., for the PUSCH) from a data source 462 and
control information (e.g., for the PUCCH) from the
controller/processor 480. The transmit processor 464 may also
generate reference symbols for a reference signal. The symbols from
the transmit processor 464 may be precoded by a TX MIMO processor
466 if applicable, further processed by the demodulators 454a
through 454r (e.g., for SC-FDM, etc.), and transmitted to the base
station 110. The transmit processor 464, TX MIMO processor 466,
modulators 454a-454r, and antennas 452a-452r may be collectively
referred to as a transmit chain of the UE. At the base station 110,
the uplink signals from the UE 120 may be received by the antennas
434, processed by the modulators 432, detected by a MIMO detector
436 if applicable, and further processed by a receive processor 438
to obtain decoded data and control information sent by the UE 120.
The receive processor 438 may provide the decoded data to a data
sink 439 and the decoded control information to the
controller/processor 440. The receive processor 438, MIMO detector
436, demodulators 432a-432t, and antennas 434a-434t may be
collectively referred to as a receive chain of the base
station.
The controllers/processors 440 and 480 may direct the operation at
the base station 110 and the UE 120, respectively. The processor
440 and/or other processors and modules at the base station 110 may
perform or direct, e.g., the execution of various processes for the
techniques described herein, such as operations 1200 and 1300,
described below with reference to FIGS. 12 and 13. The processor
480 and/or other processors and modules at the UE 120 may also
perform or direct, e.g., the execution of the functional blocks
illustrated in FIG. 12, and/or other processes for the techniques
described herein. The memories 442 and 482 may store data and
program codes for the base station 110 and the UE 120,
respectively. A scheduler 444 may schedule UEs for data
transmission on the downlink and/or uplink.
FIG. 5 is a block diagram of an example transceiver front end 500,
such as transceiver front ends 222, 254 in FIG. 2, in which aspects
of the present disclosure may be practiced. The transceiver front
end 500 includes a transmit (TX) path 502 (also known as a transmit
chain) for transmitting signals via one or more antennas and a
receive (RX) path 504 (also known as a receive chain) for receiving
signals via the antennas. When the TX path 502 and the RX path 504
share an antenna 503, the paths may be connected with the antenna
via an interface 506, which may include any of various suitable RF
devices, such as a duplexer, a switch, a diplexer, and the
like.
Receiving in-phase (I) or quadrature (Q) baseband analog signals
from a digital-to-analog converter (DAC) 508, the TX path 502 may
include a baseband filter (BBF) 510, a mixer 512, a driver
amplifier (DA) 514, and a power amplifier (PA) 516. The BBF 510,
the mixer 512, and the DA 514 may be included in a radio frequency
integrated circuit (RFIC), while the PA 516 may be external to the
RFIC. In some aspects of the present disclosure, the BBF 510 may
include a tunable active filter as described below. The BBF 510
filters the baseband signals received from the DAC 508, and the
mixer 512 mixes the filtered baseband signals with a transmit local
oscillator (LO) signal to convert the baseband signal of interest
to a different frequency (e.g., upconvert from baseband to RF).
This frequency conversion process produces the sum and difference
frequencies of the LO frequency and the frequency of the signal of
interest. The sum and difference frequencies are referred to as the
beat frequencies. The beat frequencies are typically in the RF
range, such that the signals output by the mixer 512 are typically
RF signals, which may be amplified by the DA 514 and/or by the PA
516 before transmission by the antenna 503.
The RX path 504 includes a low noise amplifier (LNA) 522, a mixer
524, and a baseband filter (BBF) 526. In some aspects of the
present disclosure, the BBF 526 may include a tunable active filter
as described below. The LNA 522, the mixer 524, and the BBF 526 may
be included in a radio frequency integrated circuit (RFIC), which
may or may not be the same RFIC that includes the TX path
components. RF signals received via the antenna 503 may be
amplified by the LNA 522, and the mixer 524 mixes the amplified RF
signals with a receive local oscillator (LO) signal to convert the
RF signal of interest to a different baseband frequency (i.e.,
downconvert). The baseband signals output by the mixer 524 may be
filtered by the BBF 526 before being converted by an
analog-to-digital converter (ADC) 528 to digital I or Q signals for
digital signal processing. In certain aspects of the present
disclosure, the PA 516 and/or LNA 522 may be implemented using a
differential amplifier.
While it is desirable for the output of an LO to remain stable in
frequency, tuning the LO to different frequencies typically entails
using a variable-frequency oscillator, which involves compromises
between stability and tunability. Contemporary systems may employ
frequency synthesizers with a voltage-controlled oscillator (VCO)
to generate a stable, tunable LO with a particular tuning range.
Thus, the transmit LO frequency may be produced by a TX frequency
synthesizer 518, which may be buffered or amplified by amplifier
520 before being mixed with the baseband signals in the mixer 512.
Similarly, the receive LO frequency may be produced by an RX
frequency synthesizer 530, which may be buffered or amplified by
amplifier 532 before being mixed with the RF signals in the mixer
524.
FIG. 6 is a diagram 600 illustrating an example of a radio protocol
architecture for the user and control planes in LTE. The radio
protocol architecture for the UE and the Node B is shown with three
layers: Layer 1, Layer 2, and Layer 3. Layer 1 (L1 layer) is the
lowest layer and implements various physical layer signal
processing functions. The L1 layer will be referred to herein as
the physical layer 606. Layer 2 (L2 layer) 608 is above the
physical layer 606 and is responsible for the link between the UE
and Node B over the physical layer 606.
In the user plane, the L2 layer 608 includes a media access control
(MAC) sublayer 610, a radio link control (RLC) sublayer 612, and a
packet data convergence protocol (PDCP) 614 sublayer, which are
terminated at the Node B on the network side. Although not shown,
the UE may have several upper layers above the L2 layer 608
including a network layer (e.g., IP layer) that is terminated at a
packet data network (PDN) gateway on the network side, and an
application layer that is terminated at the other end of the
connection (e.g., far end UE, server, etc.).
The PDCP sublayer 614 provides multiplexing between different radio
bearers and logical channels. The PDCP sublayer 614 also provides
header compression for upper layer data packets to reduce radio
transmission overhead, security by ciphering the data packets, and
handover support for UEs between Node Bs. The RLC sublayer 612
provides segmentation and reassembly of upper layer data packets,
retransmission of lost data packets, and reordering of data packets
to compensate for out-of-order reception due to hybrid automatic
repeat request (HARQ). The MAC sublayer 610 provides multiplexing
between logical and transport channels. The MAC sublayer 610 is
also responsible for allocating the various radio resources (e.g.,
resource blocks) in one cell among the UEs. The MAC sublayer 610 is
also responsible for HARQ operations.
In the control plane, the radio protocol architecture for the UE
and Node B is substantially the same for the physical layer 606 and
the L2 layer 608 with the exception that there is no header
compression function for the control plane. The control plane also
includes a radio resource control (RRC) sublayer 616 in Layer 3 (L3
layer). The RRC sublayer 616 is responsible for obtaining radio
resources (i.e., radio bearers) and for configuring the lower
layers using RRC signaling between the Node B and the UE.
FIG. 7 shows two exemplary subframe formats 710 and 720 for the
downlink with the normal cyclic prefix. The available time
frequency resources for the downlink may be partitioned into
resource blocks. Each resource block may cover 12 subcarriers in
one slot and may include a number of resource elements. Each
resource element may cover one subcarrier in one symbol period and
may be used to send one modulation symbol, which may be a real or
complex value.
Subframe format 710 may be used for a Node B equipped with two
antennas. A CRS may be transmitted from antennas 0 and 1 in symbol
periods 0, 4, 7 and 11. A reference signal is a signal that is
known a priori by a transmitter and a receiver and may also be
referred to as a pilot. A CRS is a reference signal that is
specific for a cell, e.g., generated based on a cell identity (ID).
In FIG. 7, for a given resource element with label R.sub.a, a
modulation symbol may be transmitted on that resource element from
antenna a, and no modulation symbols may be transmitted on that
resource element from other antennas. Subframe format 720 may be
used for a Node B equipped with four antennas. A CRS may be
transmitted from antennas 0 and 1 in symbol periods 0, 4, 7 and 11
and from antennas 2 and 3 in symbol periods 1 and 8. For both
subframe formats 710 and 720, a CRS may be transmitted on evenly
spaced subcarriers, which may be determined based on cell ID.
Different Node Bs may transmit their CRSs on the same or different
subcarriers, depending on their cell IDs. For both subframe formats
710 and 720, resource elements not used for the CRS may be used to
transmit data (e.g., traffic data, control data, and/or other
data).
The PSS, SSS, CRS and PBCH in LTE are described in 3GPP TS 36.211,
entitled "Evolved Universal Terrestrial Radio Access (E-UTRA);
Physical Channels and Modulation," which is publicly available.
An interlace structure may be used for each of the downlink and
uplink for FDD in LTE. For example, Q interlaces with indices of 0
through Q-1 may be defined, where Q may be equal to 4, 6, 8, 10, or
some other value. Each interlace may include subframes that are
spaced apart by Q frames. In particular, interlace q may include
subframes q, q+Q, q+2Q, etc., where q.di-elect cons.{0, . . . ,
Q-1}.
The wireless network may support hybrid automatic retransmission
(HARQ) for data transmission on the downlink and uplink. For HARQ,
a transmitter (e.g., a Node B) may send one or more transmissions
of a packet until the packet is decoded correctly by a receiver
(e.g., a UE) or some other termination condition is encountered.
For synchronous HARQ, all transmissions of the packet may be sent
in subframes of a single interlace. For asynchronous HARQ, each
transmission of the packet may be sent in any subframe.
A UE may be located within the coverage area of multiple Node Bs.
One of these Node Bs may be selected to serve the UE. The serving
Node B may be selected based on various criteria such as received
signal strength, received signal quality, pathloss, etc. Received
signal quality may be quantified by a
signal-to-noise-and-interference ratio (SINR), or a reference
signal received quality (RSRQ), or some other metric. The UE may
operate in a dominant interference scenario in which the UE may
observe high interference from one or more interfering Node Bs.
NR cell may refer to a cell operating according in the NR network.
A NR Node B (e.g., Node B 110) may correspond to one or multiple
transmission reception points (TRPs). As used herein, a cell may
refer to a combination of downlink (and potentially also uplink)
resources. The linking between the carrier frequency of the
downlink resources and the carrier frequency of the uplink
resources is indicated in the system information (SI) transmitted
on the downlink resources. For example, system information can be
transmitted in a physical broadcast channel (PBCH) carrying a
master information block (MIB).
NR RAN architecture may include a central unit (CU) (e.g., network
controller 130). The CU may be an Access node controller (ANC). The
CU terminates backhaul interface to RAN-CN, terminates backhaul
interface to neighbor RAN node. The RAN may include a Distributed
unit that may be one or more TRPs that may be connected to one or
more ANCs (not shown). TRPs may advertise System Information (e.g.,
Global TRP ID), may include PDCP/RLC/MAC functions, may comprise
one or more antenna ports, may be configured to individually
(dynamic selection) or jointly (joint transmission), and may serve
traffic to the UE.
Heterogeneous numerology wireless communication systems may refer
to systems in which UEs may be asynchronous, have different
intercarrier spacing and/or have different cyclic prefix lengths.
According to aspects of the present disclosure, tones for different
numerologies may be aligned. A numerology may be based on a
subcarrier spacing and a tone shift. As described herein,
regardless of the numerology, the tones from the heterogeneous
numerology wireless systems may be frequency-aligned.
According to aspects of the present disclosure, in a beamforming
system, a broadcast signal transmitted in a particular direction
(e.g., from a BS) may only reach a subset of UEs or other devices.
For dynamic TDD operation, a transmitter may transmit a slot or
frame format indicator to indicate the slot or frame structure for
the next N slots or subframes. However, multiple users (e.g., UEs,
BSs) may be scheduled in the N slots or subframes, and the users
may share the transmission resources (e.g., the available
frequencies for the N slots or subframes) by using TDM or FDM.
Those users may have different beamforming or beam pairing
association(s) with a transmitter, such as an eNB or a gNB. The
transmitter (e.g., a BS, an eNB, a gNB) may transmit a slot or
frame format indicator in a few OFDM symbols at the beginning of
the N slots or subframes. For non-beamforming systems, transmitting
one such indicator (e.g., broadcast to all devices in range) may be
sufficient.
FIG. 8 is a diagram 800 showing an example of a DL-centric
subframe. The DL-centric subframe may include a control portion
802. The control portion 802 may exist in the initial or beginning
portion of the DL-centric subframe. The control portion 802 may
include various scheduling information and/or control information
corresponding to various portions of the DL-centric subframe. In
some configurations, the control portion 802 may be a physical DL
control channel (PDCCH), as indicated in FIG. 8. The DL-centric
subframe may also include a DL data portion 804. The DL data
portion 804 may sometimes be referred to as the payload of the
DL-centric subframe. The DL data portion 804 may include the
communication resources utilized to communicate DL data from the
scheduling entity (e.g., UE or BS) to the subordinate entity (e.g.,
UE). In some configurations, the DL data portion 804 may be a
physical DL shared channel (PDSCH).
The DL-centric subframe may also include a common UL portion 806.
The common UL portion 806 may sometimes be referred to as an UL
burst, a common UL burst, and/or various other suitable terms. The
common UL portion 806 may include feedback information
corresponding to various other portions of the DL-centric subframe.
For example, the common UL portion 806 may include feedback
information corresponding to the control portion 802. Non-limiting
examples of feedback information may include an ACK signal, a NACK
signal, a HARQ indicator, and/or various other suitable types of
information. The common UL portion 806 may include additional or
alternative information, such as information pertaining to random
access channel (RACH) procedures, scheduling requests (SRs), and
various other suitable types of information. As illustrated in FIG.
8, the end of the DL data portion 804 may be separated in time from
the beginning of the common UL portion 806 by a guard period 808.
This guard period may sometimes be referred to as a gap, a guard
interval, and/or various other suitable terms. This guard period
provides time for the switch-over from DL communication (e.g.,
reception operation by the subordinate entity (e.g., UE)) to UL
communication (e.g., transmission by the subordinate entity (e.g.,
UE)). One of ordinary skill in the art will understand that the
foregoing is merely one example of a DL-centric subframe and
alternative structures having similar features may exist without
necessarily deviating from the aspects described herein.
FIG. 9 is a diagram 900 showing an example of an UL-centric
subframe. The UL-centric subframe may include a control portion
902. The control portion 902 may exist in the initial or beginning
portion of the UL-centric subframe. The control portion 902 in FIG.
9 may be similar to the control portion described above with
reference to FIG. 8. The UL-centric subframe may also include an UL
data portion 904. The UL data portion 904 may sometimes be referred
to as the payload of the UL-centric subframe. The UL portion may
refer to the communication resources utilized to communicate UL
data from the subordinate entity (e.g., UE) to the scheduling
entity (e.g., UE or BS). In some configurations, the control
portion 902 may be a physical DL control channel (PDCCH).
As illustrated in FIG. 9, the end of the control portion 902 may be
separated in time from the beginning of the UL data portion 904 by
a guard period 908. This time separation may sometimes be referred
to as a gap, guard period, guard interval, and/or various other
suitable terms. This separation provides time for the switch-over
from DL communication (e.g., reception operation by the scheduling
entity) to UL communication (e.g., transmission by the scheduling
entity). The UL-centric subframe may also include a common UL
portion 906. The common UL portion 906 in FIG. 9 may be similar to
the common UL portion 806 described above with reference to FIG. 8.
The common UL portion 906 may additional or alternative include
information pertaining to channel quality indicator (CQI), sounding
reference signals (SRSs), and various other suitable types of
information. One of ordinary skill in the art will understand that
the foregoing is merely one example of an UL-centric subframe and
alternative structures having similar features may exist without
necessarily deviating from the aspects described herein.
In some circumstances, two or more subordinate entities (e.g., UEs)
may communicate with each other using sidelink signals. Real-world
applications of such sidelink communications may include public
safety, proximity services, UE-to-network relaying,
vehicle-to-vehicle (V2V) communications, Internet of Everything
(IoE) communications, IoT communications, mission-critical mesh,
and/or various other suitable applications. Generally, a sidelink
signal may refer to a signal communicated from one subordinate
entity (e.g., UE1) to another subordinate entity (e.g., UE2)
without relaying that communication through the scheduling entity
(e.g., UE or BS), even though the scheduling entity may be utilized
for scheduling and/or control purposes. In some examples, the
sidelink signals may be communicated using a licensed spectrum
(unlike wireless local area networks, which typically use an
unlicensed spectrum).
A UE may operate in various radio resource configurations,
including a configuration associated with transmitting pilots using
a dedicated set of resources (e.g., a radio resource control (RRC)
dedicated state, etc.) or a configuration associated with
transmitting pilots using a common set of resources (e.g., an RRC
common state, etc.). When operating in the RRC dedicated state, the
UE may select a dedicated set of resources for transmitting a pilot
signal to a network. When operating in the RRC common state, the UE
may select a common set of resources for transmitting a pilot
signal to the network. In either case, a pilot signal transmitted
by the UE may be received by one or more network access devices,
such as an AN, or a DU, or portions thereof. Each receiving network
access device may be configured to receive and measure pilot
signals transmitted on the common set of resources, and also
receive and measure pilot signals transmitted on dedicated sets of
resources allocated to the UEs for which the network access device
is a member of a monitoring set of network access devices for the
UE. One or more of the receiving network access devices, or a CU to
which receiving network access device(s) transmit the measurements
of the pilot signals, may use the measurements to identify serving
cells for the UEs, or to initiate a change of serving cell for one
or more of the UEs.
Example Handling Power Transitions in New Radio
It may be desirable for transmitters in an NR (e.g., 5.sup.th
Generation Technology Forum (5GTF)) wireless communications system
to change a power level in the middle of transmissions. Changing a
power level in the middle of a transmission may cause a loss of
phase coherence (e.g., of the transmitted waveform). For example,
phase coherence may be lost if a power change is not implemented
digitally, but is instead implemented via a change in an analog
gain stage(s) of a transmit chain. Loss of phase coherence may be
more severe in uplink (UL) transmissions than in downlink (DL)
transmissions, because mobile devices (e.g., UEs) may have
implementation constraints that base stations (e.g., next
generation NodeBs (gNBs)) do not have. For example, an amount of
digital gain that a mobile device can generate may be less than an
amount of digital gain that a base station can generate.
According to aspects of the present disclosure described herein, a
device (e.g., a UE or a BS) may transmit a transmission with
different power levels for different portions of the transmission
(e.g., different power levels for reference signals and data
incorporated in an orthogonal frequency domain multiplexing (OFDM)
symbol), and the device may take one or more actions to mitigate a
phase coherence loss that may result from the changing power level
of the transmission. A phase coherence loss may cause a receiver to
experience difficulty in receiving and decoding the transmission,
so mitigating the potential phase coherence loss may improve data
throughput rates and/or reduce error rates of communications.
FIGS. 10A-10C illustrate exemplary transmission timelines 1000,
1020, and 1050 illustrative of potential problems that can occur
when a device transmits a transmission with different power levels,
according to aspects of the present disclosure. In the exemplary
timeline 1000, an exemplary ideal waveform 1004 is transmitted in a
transmission time interval (TTI) 1002 by an idealized (i.e., not an
actual) transmitter. It may be noted that the idealized transmitter
does not transmit outside of the TTI 1002 in the exemplary timeline
1000. An idealized transmitter generates the ideal waveform 1004
beginning at 1006 and ending at 1008, while any waveforms generated
before 1006 or after 1008 (i.e. in TTIs other than TTI 1002) are
completely unaffected by the transmitter's activity during TTI
1002, i.e., any waveforms generated before 1006 or after 1008 are
completely independent of the waveform 1004.
In the exemplary timeline 1020 shown in FIG. 10B, an exemplary
waveform 1024 is transmitted by an exemplary transmitter (i.e., an
actual transmitter, such as a transmitter in UE 120, shown in FIGS.
1 and 4, and not an idealized transmitter, as referred to in FIG.
10A) in the TTI 1002. The exemplary transmitter makes a spurious
transmission 1022 before the TTI 1002 begins at 1006, for example,
when various components of the transmitter are ramping up to a
desired power level. It may be noted that the waveform 1024 is
similar to the waveform 1004, shown in FIG. 10A, but the
transmitter transmits the spurious transmission 1022 outside of the
TTI.
In the exemplary timeline 1050 shown in FIG. 10C, an exemplary
waveform 1054 is transmitted by an exemplary transmitter (i.e., an
actual transmitter, such as a transmitter in UE 120, shown in FIGS.
1 and 4, and not an idealized transmitter, as referred to in FIG.
10A) in the TTI 1002. The exemplary transmitter makes a spurious
transmission 1052 during the TTI 1002 (i.e., after the TTI begins
at 1006), for example, when various components of the transmitter
are ramping up to a desired power level. It may be noted that the
waveform 1054 differs from the waveform 1004, shown in FIG. 10A,
due to the spurious transmission 1052, but the transmitter does not
transmit outside (i.e., before the beginning 1006 or after the end
1008) of the TTI.
FIG. 11 is a diagram 1100 illustrating an example of an UL
transmission (e.g., a PUSCH), according to aspects of the present
disclosure. A UE may transmit an uplink transmission in a slot 1102
on a set of subcarriers 1104. A resource grid may be used to
represent resource elements of a resource block. As illustrated, a
resource block may contain 12 consecutive subcarriers in the
frequency domain and 7 consecutive OFDM symbols in the time domain,
or 84 resource elements. As illustrated at 1106, the UE may
transmit reference signals (e.g., DMRS) on some resource elements
of an OFDM symbol, while leaving other REs of the OFDM symbol
blank. The UE may transmit data on some or all of the other REs, as
shown at 1108.
In the exemplary timeline 1120, the UE leaves the beginning of the
first RE 1122 blank, as exemplified by the straight line at 1130.
The UE transmits an exemplary waveform 1132 to convey the data of
the second RE 1124. Due to the transition from the first (blank) RE
1122 to the second (data) RE 1124, the UE makes a spurious
transmission 1134 before the second RE begins at 1126, for example,
when various components of a transmitter of the UE are ramping up
to a desired power level, similar to the spurious transmission
shown in FIG. 10B, described above. The spurious transmission 1134
may interfere with other transmissions that are occurring in that
same RE or cause a loss of phase coherence in the transmitted
waveform, but does not alter the data transmitted in the RE
1124.
In the exemplary timeline 1150 the UE leaves the first RE 1152
blank, as exemplified by the straight line at 1160. The UE
transmits an exemplary wave form 1164 to convey the data of the
second RE 1154. Due to the transition from the first (blank) RE
1152 to the second (data) RE 1154, the UE makes a spurious
transmission 1164 at the beginning 1156 of the second RE, for
example, when various components of a transmitter of the UE are
ramping up to a desired power level, similar to the spurious
transmission shown in FIG. 10C, described above. The spurious
transmission 1164 may cause a loss of phase coherence in the
transmitted waveform or a loss of some data in the transmission,
but does not interfere with other transmissions in the RE 1152.
Thus, a UE transmitting the exemplary uplink transmission
illustrated in FIG. 11 may generate a spurious transmission in an
RE that the UE should leave blank, possibly interfering with
transmissions by other UEs on that RE, or the UE may generate a
spurious transmission in an RE in which the UE is transmitting
data, possibly causing a receiver of the transmission to
misinterpret the data, e.g., by failing to decode the transmission.
In both cases, the sudden change in the power level of the
transmission may cause a loss of phase coherence in the generated
waveform.
It should be noted that, due to the much shorter slot-lengths used
in NR communications systems as compared to previously known
communications systems, the spurious transmissions described above
may occur in a larger portion of an RE than if the same transmitter
were transmitting in previously known (e.g., LTE) communications
systems.
According to aspects of the present disclosure, a wireless device
may mitigate phase coherence loss related to sudden transitions in
transmit power in a transmission by manipulating digital gains in a
digital portion of a transmit chain, while leaving analog gains in
an analog portion of the transmit chain unchanged.
FIG. 12 illustrates example operations 1200 for wireless
communications that may be performed by a wireless device,
according to aspects of the present disclosure. The UE may be UE
120 or BS 110, shown in FIG. 1, which may include one or more
components illustrated in FIG. 4.
Operations 1200 begin at block 1202 with the wireless device
determining to use a first transmit power during a first portion of
a transmission and a second transmit power during a second portion
of the transmission. For example, UE 120 (shown in FIG. 1)
determines to use a first transmit power during a first portion of
a PUSCH (e.g., a blank RE in a symbol period containing a
demodulation reference signal (DMRS) on other REs of the symbol
period) and a second transmit power (e.g., higher than the first
transmit power) during a second portion of the PUSCH (e.g., an RE
containing data).
At block 1204, operations 1200 continue with the wireless device
mitigating a potential phase coherence loss associated with a
changing from the first transmit power to the second transmit
power. Continuing the example from above, UE 120 mitigates (e.g.,
increasing digital gains associated with the REs in the symbol
period containing the blank REs and DMRS so as to allow analog
gains of a transmit chain to remain unchanged from symbol period to
symbol period; or selecting a sequence with a low
peak-to-average-power-ratio (PAPR) for the DMRS) a potential phase
coherence loss associated with a changing from the first transmit
power to the second transmit power).
Operations 1200 continue at block 1206 with the wireless device
transmitting the first portion of the transmission using the first
transmit power and the second portion of the transmission using the
second transmit power. Continuing the example from above, UE 120
transmits the first portion of the PUSCH (e.g., the blank RE in the
symbol period containing the DMRS on other REs of the symbol
period) using the first transmit power and the second portion of
the PUSCH (e.g., the RE containing data) using the second transmit
power.
FIG. 13 illustrates example operations 1300 for wireless
communications that may be performed by a wireless device,
according to aspects of the present disclosure. The wireless device
may be BS 110 shown in FIG. 1 or a UE that schedules communications
for other UEs (e.g., in device-to-device communications), which may
include one or more components illustrated in FIG. 4.
Operations 1300 begin at block 1302 with the wireless device
transmitting a first grant scheduling a UE to transmit a first
transmission, wherein the UE changes from using a first transmit
power during a first portion of the first transmission to a second
transmit power during a second portion of the first transmission.
For example, BS 110 (shown in FIG. 1) transmits a first grant
scheduling UE 120 to transmit a first transmission (e.g., a PUSCH),
wherein the UE changes from using a first transmit power during a
first portion of the first transmission (e.g., an RE containing
data) to a second transmit power during a second portion of the
first transmission (e.g., an RE containing a DMRS).
At block 1304, operations 1300 continue with the wireless device
transmitting a second grant scheduling the UE to transmit a second
transmission comprising an indication of at least one of the first
transmit power or the second transmit power. Continuing the example
from above, the BS 110 transmits a second grant scheduling the UE
120 to transmit a second transmission (e.g., a PUCCH) comprising an
indication (e.g., a bit in a field of the PUCCH) of the first
transmit power (e.g., the transmit power of the RE containing the
data).
Operations 1300 continue at block 1306 with the wireless device
receiving the first transmission from the UE, based on the
indication. Continuing the example from above, the BS 110 receives
the PUSCH from UE 120, based on the indication of the first
transmit power from block 1304. That is, the BS receives the PUSCH
based on the transmit power indicated by the UE in the second
transmission that is scheduled by the second grant.
According to aspects of the present disclosure, in NR wireless
communications systems, in some OFDM symbols, certain REs have to
be left empty (i.e., transmitted with zero power). Transmitting an
OFDM symbol with some REs left empty may be an example of changing
from using a first transmit power during a first portion of a
transmission to a second transmit power during a second portion of
the transmission, as described above with reference to block 1202
in FIG. 12. For example, some REs may be occupied by transmissions
by other UEs, such as comb-based SRS transmission, wherein a UE may
be assigned all combs on one OFDM symbol but a subset of the combs
on the next OFDM symbol. In another example, some REs may be
reserved for forward compatibility, and UEs following future
versions of the air-interface specifications may use the reserved
REs. In yet another example, some REs may be reserved for
ultra-reliable low latency communications (URLLC) transmission(s)
by other UEs.
In aspects of the present disclosure, if some REs of a transmission
are blanked while other REs are sent without any change, overall
transmit power in the OFDM symbol is different from transmit power
of OFDM symbols without any blanking. This difference in transmit
power has a potential to cause a phase discontinuity (e.g., a phase
coherence loss, as mentioned above in block 1204 in FIG. 12) in
transmissions by a device.
According to aspects of the present disclosure, a transmitting
device may blank an entire OFDM symbol, if certain REs of the OFDM
symbol have to be blanked. Blanking an entire OFDM symbol may be an
example of taking action to mitigate a potential phase coherence
loss associated with the changing from the first transmit power to
the transmit power, as described above with reference to block 1204
in FIG. 12.
In aspects of the present disclosure, blanking of an entire OFDM
symbol may be done digitally (e.g., in a digital domain symbol,
such as the I and Q digital signals obtained by the DAC 508 shown
in FIG. 5) by a wireless device. Blanking an entire OFDM symbol
digitally may result in no loss of phase coherence, because other
components of a transmit chain remain energized at a same energy
level. However, blanking an entire OFDM symbol may waste
transmission resources.
According to aspects of the present disclosure, there may be some
residual transmit power transmitted from analog components (e.g.,
the PA) of a transmit chain of a device that digitally blanks an
entire OFDM symbol.
In aspects of the present disclosure, communications systems
operating according to disclosed techniques may use new rules
limiting these emissions (e.g., residual transmit power) that may
be more relaxed than the transmit power limits when the UE is more
"fully" turned off (i.e., off for longer contiguous time
durations).
According to aspects of the present disclosure, a transmitting
device may blank REs in a digital domain signal prior to converting
the digital domain signal to an analog domain signal for
transmission. Blanking REs in a digital domain signal prior to
converting the digital domain signal to an analog domain signal for
transmission may be an example of taking action to mitigate a
potential phase coherence loss associated with the changing from
the first transmit power to the transmit power, as described above
with reference to block 1204 in FIG. 12. If a device blanks REs in
a digital domain, though a total transmit power changes, analog
gains of the transmit chain are unchanged, resulting in no loss of
phase coherence. This may cause suboptimal analog gain settings for
the resulting transmit power. The suboptimal analog gain setting
may impact quality (e.g., calculation of error vector magnitude
(EVM)) of the resulting transmission.
According to aspects of the present disclosure, a transmitting
device may boost power of un-blanked REs in a digital domain signal
prior to converting the digital domain signal to an analog domain
signal for transmission, in order to preserve overall transmit
power at a consistent level. Boosting power of un-blanked REs in a
digital domain signal prior to converting the digital domain signal
to an analog domain signal for transmission may be an example of
taking action to mitigate a potential phase coherence loss
associated with the changing from the first transmit power to the
second transmit power, as described above with reference to block
1204 in FIG. 12. Boosting power of un-blanked REs in a digital
domain signal may result in analog gains of a transmit chain of the
device remaining unchanged and total transmit power of the
transmission being unchanged from symbol period to symbol period.
If analog gains of the transmit chain remain unchanged, then there
may be no loss of phase coherence. In aspects of the present
disclosure, boosting power of un-blanked REs may not always be
possible, for example, if digital domain gains of a transmitting
device are already at their maximum settings.
In aspects of the present disclosure, a device taking action to
mitigate a potential phase coherence loss may use a combination of
the techniques described earlier. For example, a device may always
boost the power of unblanked REs to keep total power unchanged,
regardless of whether or not such boosting can be done purely
digitally, by incurring some possible performance loss due to loss
of phase coherence whenever digital boosting is infeasible. In such
a case, the receiving device knows the power level of the OFDM
symbols containing the blanked REs relative to other OFDM symbols
without blanked REs. In another example, a transmitting device may
boost power only to the extent possible digitally (e.g., to the
maximum setting of the digital domain gains) and keep analog gains
unchanged. A receiving device may not then know the amount of boost
applied, as the receiver is typically unaware of digital settings
at the transmitter.
According to aspects of the present disclosure, digital domain gain
settings of a transmitting device may be dynamic, depending on a
current transmission power level and other factors, such as TX
chain selection across multiple radio access technologies (RATs) at
the transmitter.
In aspects of the present disclosure, a transmitting device may
signal a level of transmit power boost applied to a transmission to
an intended receiver of the transmission. Signaling of a level of
transmit power may be important to a receiver for certain types of
transmissions. For example, for SRS transmissions, the relative
transmit power boosts applied on different OFDM symbols are used by
a receiver of the SRS to compare channel quality estimated from the
SRS. In another example, for data transmissions, especially long
ones, a change in power level for one OFDM symbol may be less
important for the receiver to know about.
According to aspects of the present disclosure, signaling of
transmit power levels may be made in a different transmission time
interval (TTI) than the transmission with the boosted transmit
power levels. For example, if SRS processing (e.g., by a base
station) is not time-critical, then SRS transmit power levels may
be indicated in a suitable `nearby in time` PUCCH transmission from
a transmitting UE.
In aspects of the present disclosure, if there is no `nearby in
time` PUCCH or UL control transmission for a UE to use to signal a
transmit power level, then a PUCCH or other UL control transmission
for signaling transmit power levels may be scheduled explicitly by
a base station. Explicit scheduling of UL control transmissions for
signaling transmit power levels may require extra overhead.
According to aspects of the present disclosure, signaling of
transmit power levels may be enabled and/or disabled, depending on
a transmission type of the transmission, including waveform,
transmission contents, and transmission power of the
transmission.
According to aspects of the present disclosure, transmitting using
pi/2 binary phase shift keying (pi/2-BPSK or .PI./2-BPSK)
modulation together with a discrete Fourier transform
single-carrier orthogonal frequency division multiplexing
(DFT-s-OFDM) waveform has a significantly lower
peak-to-average-power-ratio (PAPR) than transmitting using
quadrature phase shift keying (QPSK) modulation. Transmitting with
pi/2-BPSK modulation and a DFT-s-OFDM waveform also has a lower
PAPR than Zadoff-Chu sequences chosen explicitly for their low PAPR
for demodulation reference signals (DMRS) in LTE UL
transmissions.
In aspects of the present disclosure, re-using Zadoff-Chu sequences
for DMRS transmissions may require special handling, because of the
Zadoff-Chu sequences having a higher PAPR than a pi/2-BPSK
DFT-s-OFDM waveform used for conveying data in a same period as the
DMRS.
In aspects of the present disclosure, if a new radio transmitting
device uses a Zadoff-Chu sequence for DMRS transmissions (e.g.,
similar to an LTE transmitting device), the transmitting device may
apply a different power amplifier (PA) back-off for DMRS (e.g.,
DMRS based on Zadoff-Chu sequences that have a higher PAPR than a
pi/2-BPSK DFT-s-OFDM waveform) REs in a transmission than the
transmitting device uses for REs conveying data in the
transmission. This may result in a different transmit power for REs
conveying data and for DMRS in the transmission, again possibly
causing a phase discontinuity (e.g., loss of phase coherence) in
the transmission.
According to aspects of the present disclosure, the same techniques
described above (e.g., blanking of an entire OFDM symbol in the
digital domain or by other techniques, blanking REs in a digital
domain signal prior to converting the digital domain signal to an
analog domain signal, and/or boosting power of un-blanked REs in a
digital domain signal prior to converting the digital domain signal
to an analog domain signal) may be used by a transmitting device to
prevent a potential loss of phase coherence between reference
signals (e.g., DMRS) in a transmission and REs conveying data in
the transmission.
In aspects of the present disclosure, a transmitting device may
change transmit power only in a digital domain signal to mitigate a
potential loss of phase coherence between reference signals (e.g.,
DMRS) in a transmission and REs conveying data in the transmission.
Additionally, a transmitting device may signal to a receiving
device a resulting ratio of data RE transmit power to DMRS RE
transmit power (e.g., a transmit power ratio (TPR)) used by the
transmitting device.
According to aspects of the present disclosure, signaling of the
resulting ratio of data RE transmit power to DMRS RE transmit power
described above may be optional in a communications system and used
only in certain conditions. Determination of whether the signaling
of the resulting ratio of data RE transmit power to DMRS transmit
power is enabled for a transmission may depend on the transmission
contents and/or power level.
In aspects of the present disclosure, signaling of the resulting
ratio of data RE transmit power to DMRS RE transmit power may be
avoided by applying a fixed TPR (less power for DMRS based on
Zadoff-Chu sequences than data on pi/2-BPSK DFT-s-OFDM waveforms,
or de-boosting of DMRS relative to data) regardless of transmit
power level, i.e., regardless of whether or not the PA is close to
saturation. In such cases, a phase discontinuity caused by the
change in transmit power can be avoided by lowering the transmit
power digitally. Further, to combat the possibility of the receiver
having difficulty estimating the channel because of the lower DMRS
power, such transmissions may use a DMRS pattern with higher DMRS
overhead, for example, more TDM DMRS OFDM symbols. The DMRS pattern
and overhead for low PAPR waveforms requiring such DMRS de-boosting
may be configured by RRC signaling, or may be implicitly derived
based on the modulation and coding scheme (MCS) and/or waveform of
the transmission. That is, the UE may determine an implicit
derivation of the DMRS pattern and overhead, based on the MCS
and/or waveform of the transmission. For example, a UE may be
configured such that when the MCS of an UL transmission from the UE
indicates the transmission is to be transmitted using pi/2-BPSK
modulation with a DFT-s-OFDM waveform, the UE is to transmit one or
more additional DMRS OFDM symbols in a time division multiplexing
manner with the data of the UL transmission. In the example, the
number of additional DMRS OFDM symbols may be indicated to the UE
by RRC signaling.
According to aspects of the present disclosure, a transmitting
device may use another DMRS sequence (i.e., other than a Zadoff-Chu
sequence) with a PAPR comparable to or lower than the PAPR of
pi/2-BPSK modulated data.
In aspects of the present disclosure, pi/2-BPSK DFT-s-OFDM
transmissions from multiple UEs may be multiplexed together in the
same RBs. That, is multiple UEs may transmit different pi/2
DFT-s-OFDM transmissions via a set of RBs. In this case, it is
desirable that DMRS included in the transmissions from the UEs be
orthogonal, so that a receiving device may differentiate between
the DMRS of each of the UEs. For DMRS based on Zadoff-Chu sequences
that are populated directly in the frequency domain (e.g., at an
input of an inverse fast Fourier transform (IFFT) in a transmit
chain), the DMRS could be orthogonalized by a combination of using
different frequency combs (e.g., each UE transmits its DMRS on an
equi-spaced, non-contiguous set of tones selected from sets of
equi-spaced, non-contiguous sets of tones that are multiplexed in
the set of RBs in a frequency division multiplexing (FDM) manner),
different OFDM symbols (e.g., each UE transmits its DMRS in a
different OFDM symbol in the set of RBs in a time division
multiplexing (TDM) manner), and/or orthogonal cover codes (OCC)
applied (e.g., each UE transmits its DMRS using a different OCC in
a code division multiplexing (CDM) manner) across time or across
frequency. For special DMRS sequences created using pi/2-BPSK
DFT-s-OFDM modulation (e.g., sequences different from Zadoff-Chu
sequences and generated to have a low PAPR comparable to the PAPR
of pi/2-BPSK modulated data symbols), both the population of the
sequence onto a comb and the application of the OCC across
frequency may result in a DMRS time-domain sequence that is not a
pi/2-BPSK waveform, thus increasing the PAPR. Hence, special
constructions may be employed in the comb and OCC application
process to avoid a PAPR increase and, if possible, preserve the
pi/2-BPSK property of the special DMRS sequences.
For example, a pi/2-BPSK sequence input to a DFT-spreading
component of a transmit chain may result in a time-interpolated
pi/2-BPSK sequence after a DFT-spreading operation and OFDM IFFT
operation of the transmit chain, when the output of the
DFT-spreading component is populated on a certain contiguous set of
tones. If the output of the DFT-spreading component is instead
populated on a comb of tones, then this low PAPR property may
continue to hold for certain combs, wherein the time domain
waveform is a time-compressed and repeated version of an
interpolated pi/2-BPSK sequence with the number of repetitions
corresponding to the comb period. For other combs, the output may
be the result of applying a time-domain phase ramp to such a
waveform. This phase ramp implies that the time domain waveform is
no longer an interpolated pi/2-BPSK waveform, and may have a worse
PAPR. To avoid this issue, the time-compressed and repeated version
of the sequence obtained when the pi/2-BPSK property is preserved
may further be processed by applying a phase-shift to the various
repetitions, with the phase shift being the same within each
repetition but different across different repetitions. In some
cases, this application of phase shifts across repetitions may
still preserve the pi/2-BPSK waveform property. In other cases,
this pi/2-BPSK waveform property may be preserved within each
repetition, although it may be lost at the time-boundary between
the repetitions. In both cases, this application of phase shifts
across repetitions shifts the waveform onto a different FDM comb
without the need to apply a continuous phase ramp that more
strongly destroys the pi/2-BPSK waveform property.
The methods disclosed herein comprise one or more steps or actions
for achieving the described method. The method steps and/or actions
may be interchanged with one another without departing from the
scope of the claims. In other words, unless a specific order of
steps or actions is specified, the order and/or use of specific
steps and/or actions may be modified without departing from the
scope of the claims.
As used herein, a phrase referring to "at least one of" a list of
items refers to any combination of those items, including single
members. As an example, "at least one of: a, b, or c" is intended
to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any
combination with multiples of the same element (e.g., a-a, a-a-a,
a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or
any other ordering of a, b, and c).
As used herein, the term "determining" encompasses a wide variety
of actions. For example, "determining" may include calculating,
computing, processing, deriving, investigating, looking up (e.g.,
looking up in a table, a database or another data structure),
ascertaining and the like. Also, "determining" may include
receiving (e.g., receiving information), accessing (e.g., accessing
data in a memory) and the like. Also, "determining" may include
resolving, selecting, choosing, establishing and the like.
The previous description is provided to enable any person skilled
in the art to practice the various aspects described herein.
Various modifications to these aspects will be readily apparent to
those skilled in the art, and the generic principles defined herein
may be applied to other aspects. Thus, the claims are not intended
to be limited to the aspects shown herein, but is to be accorded
the full scope consistent with the language claims, wherein
reference to an element in the singular is not intended to mean
"one and only one" unless specifically so stated, but rather "one
or more." Unless specifically stated otherwise, the term "some"
refers to one or more. All structural and functional equivalents to
the elements of the various aspects described throughout this
disclosure that are known or later come to be known to those of
ordinary skill in the art are expressly incorporated herein by
reference and are intended to be encompassed by the claims.
Moreover, nothing disclosed herein is intended to be dedicated to
the public regardless of whether such disclosure is explicitly
recited in the claims. No claim element is to be construed under
the provisions of 35 U.S.C. .sctn. 112, sixth paragraph, unless the
element is expressly recited using the phrase "means for" or, in
the case of a method claim, the element is recited using the phrase
"step for."
The various operations of methods described above may be performed
by any suitable means capable of performing the corresponding
functions. The means may include various hardware and/or software
component(s) and/or module(s), including, but not limited to a
circuit, an application specific integrated circuit (ASIC), or
processor. Generally, where there are operations illustrated in
figures, those operations may have corresponding counterpart
means-plus-function components with similar numbering.
The various illustrative logical blocks, modules and circuits
described in connection with the present disclosure may be
implemented or performed with a general purpose processor, a
digital signal processor (DSP), an application specific integrated
circuit (ASIC), a field programmable gate array (FPGA) or other
programmable logic device (PLD), discrete gate or transistor logic,
discrete hardware components, or any combination thereof designed
to perform the functions described herein. A general-purpose
processor may be a microprocessor, but in the alternative, the
processor may be any commercially available processor, controller,
microcontroller, or state machine. A processor may also be
implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
If implemented in hardware, an example hardware configuration may
comprise a processing system in a wireless node. The processing
system may be implemented with a bus architecture. The bus may
include any number of interconnecting buses and bridges depending
on the specific application of the processing system and the
overall design constraints. The bus may link together various
circuits including a processor, machine-readable media, and a bus
interface. The bus interface may be used to connect a network
adapter, among other things, to the processing system via the bus.
The network adapter may be used to implement the signal processing
functions of the PHY layer. In the case of a user terminal 120 (see
FIG. 1), a user interface (e.g., keypad, display, mouse, joystick,
etc.) may also be connected to the bus. The bus may also link
various other circuits such as timing sources, peripherals, voltage
regulators, power management circuits, and the like, which are well
known in the art, and therefore, will not be described any further.
The processor may be implemented with one or more general-purpose
and/or special-purpose processors. Examples include
microprocessors, microcontrollers, DSP processors, and other
circuitry that can execute software. Those skilled in the art will
recognize how best to implement the described functionality for the
processing system depending on the particular application and the
overall design constraints imposed on the overall system.
If implemented in software, the functions may be stored or
transmitted over as one or more instructions or code on a
computer-readable medium. Software shall be construed broadly to
mean instructions, data, or any combination thereof, whether
referred to as software, firmware, middleware, microcode, hardware
description language, or otherwise. Computer-readable media include
both computer storage media and communication media including any
medium that facilitates transfer of a computer program from one
place to another. The processor may be responsible for managing the
bus and general processing, including the execution of software
modules stored on the machine-readable storage media. A
computer-readable storage medium may be coupled to a processor such
that the processor can read information from, and write information
to, the storage medium. In the alternative, the storage medium may
be integral to the processor. By way of example, the
machine-readable media may include a transmission line, a carrier
wave modulated by data, and/or a computer readable storage medium
with instructions stored thereon separate from the wireless node,
all of which may be accessed by the processor through the bus
interface. Alternatively, or in addition, the machine-readable
media, or any portion thereof, may be integrated into the
processor, such as the case may be with cache and/or general
register files. Examples of machine-readable storage media may
include, by way of example, RAM (Random Access Memory), flash
memory, ROM (Read Only Memory), PROM (Programmable Read-Only
Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM
(Electrically Erasable Programmable Read-Only Memory), registers,
magnetic disks, optical disks, hard drives, or any other suitable
storage medium, or any combination thereof. The machine-readable
media may be embodied in a computer-program product.
A software module may comprise a single instruction, or many
instructions, and may be distributed over several different code
segments, among different programs, and across multiple storage
media. The computer-readable media may comprise a number of
software modules. The software modules include instructions that,
when executed by an apparatus such as a processor, cause the
processing system to perform various functions. The software
modules may include a transmission module and a receiving module.
Each software module may reside in a single storage device or be
distributed across multiple storage devices. By way of example, a
software module may be loaded into RAM from a hard drive when a
triggering event occurs. During execution of the software module,
the processor may load some of the instructions into cache to
increase access speed. One or more cache lines may then be loaded
into a general register file for execution by the processor. When
referring to the functionality of a software module below, it will
be understood that such functionality is implemented by the
processor when executing instructions from that software
module.
Also, any connection is properly termed a computer-readable medium.
For example, if the software is transmitted from a website, server,
or other remote source using a coaxial cable, fiber optic cable,
twisted pair, digital subscriber line (DSL), or wireless
technologies such as infrared (IR), radio, and microwave, then the
coaxial cable, fiber optic cable, twisted pair, DSL, or wireless
technologies such as infrared, radio, and microwave are included in
the definition of medium. Disk and disc, as used herein, include
compact disc (CD), laser disc, optical disc, digital versatile disc
(DVD), floppy disk, and Blu-ray.RTM. disc where disks usually
reproduce data magnetically, while discs reproduce data optically
with lasers. Thus, in some aspects computer-readable media may
comprise non-transitory computer-readable media (e.g., tangible
media). In addition, for other aspects computer-readable media may
comprise transitory computer-readable media (e.g., a signal).
Combinations of the above should also be included within the scope
of computer-readable media.
Thus, certain aspects may comprise a computer program
product/computer readable medium for performing the operations
presented herein. For example, such a computer program product may
comprise a computer-readable medium having instructions stored
(and/or encoded) thereon, the instructions being executable by one
or more processors to perform the operations described herein.
Further, it should be appreciated that modules and/or other
appropriate means for performing the methods and techniques
described herein can be downloaded and/or otherwise obtained by a
user terminal and/or base station as applicable. For example, such
a device can be coupled to a server to facilitate the transfer of
means for performing the methods described herein. Alternatively,
various methods described herein can be provided via storage means
(e.g., RAM, ROM, a physical storage medium such as a compact disc
(CD) or floppy disk, etc.), such that a user terminal and/or base
station can obtain the various methods upon coupling or providing
the storage means to the device. Moreover, any other suitable
technique for providing the methods and techniques described herein
to a device can be utilized.
It is to be understood that the claims are not limited to the
precise configuration and components illustrated above. Various
modifications, changes and variations may be made in the
arrangement, operation and details of the methods and apparatus
described above without departing from the scope of the claims.
* * * * *